In the last few years evidence has accumulated that much genetic variation exists at protein loci which is not detectable by usual electrophoretic procedures. In my own laboratory I have detected such cryptic alleles by gel sieving analysis. I propose to further examine this class of protein variation, assessing its genetic and biochemical character. Possible functional differences between these variant proteins will be examined by spectrophotometer assay, estimating the binding constants of substrate, cofactor, and effector molecules as functions of temperature. I have suggested that enzyme polymorphism in intermediary metabolism may represent a means of physiologically compensating for environmental variation. This suggests that selection acts on coordinate metabolic phenotypes, and predicts significant disequilibrium in allele frequencies. I find just such coordinate complexes of alleles among alpine butterflies. In a parallel series of investigations I will characterize the kinetic properties of the allozymes involved in these coordinate gene complexes. In particular, I will look for similarity among the enzyme alleles of a coordinate complex in their kinetic response to environmental variables such as temperature. This will involve detailed kinetic analysis, and will focus initially on four reactions involved in the mobilization and utilization of glucose.